Metachronous B-Cell Acute Lymphoblastic Leukemia After Localized Neuroblastoma Treated Without Cytotoxic Therapy: A Case Report.

A 7-month-old infant developed therapy-independent acute lymphoblastic leukemia (ALL) 8 months after complete resection of an International Neuroblastoma Risk Group (INRG) Stage L1 adrenal neuroblastoma (N-MYC nonamplified) treated with surgery alone. The patient presented with leukemia cutis and discordant bone marrow findings: the initial aspirate revealed > 90% lymphoblasts (CD45+/CD19+/CD10+/TdT+), whereas two subsequent marrow examinations showed normocellular hematopoiesis, suggesting spatially heterogeneous marrow involvement with predominant extramedullary disease. Skin biopsy confirmed leukemic infiltration (PAX5+/TdT+/CD34+/CD10-). Germline testing was not available. Standard-risk chemotherapy achieved complete remission, and the patient is currently receiving maintenance therapy. This case highlights that second primary ALL can occur in the absence of cytotoxic therapy after neuroblastoma and underscores the need for long-term surveillance and consideration of genetic evaluation in selected patients.